Synthesis of quaternary ammonium lignin and its adsorption properties on AuCl4-

Abstract

Quaternary ammonium lignin was synthesized from rice straw after phenolization, crosslinking and amination. Its adsorption properties for AuCl4- were investigated. The adsorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), thermogravimetric analysis and differential scanning calorimetry (TG-DSC). The effects of initial concentration of AuCl4-, concentration of hydrochloric acid and adsorption time on the effect of adsorption for AuCl4- were discussed. The results show that the quaternary ammonium lignin has excellent thermal stability and its surface is irregularly rough and porous. The maximum adsorption capacity is 3.27 mol·kg-1 when the concentration of hydrochloric acid is 0.5 mol·L-1, the initial concentration of AuCl4- is 6.0 mmol·L-1 and the adsorption time is 100 h. The equilibrium time of adsorption for AuCl4- is 360 min when the concentration of AuCl4- is 1 mmol·L-1, the concentration of hydrochloric acid is 0.5 mol·L-1. Moreover, AuCl4- was reduced to elemental gold by the phenolic hydroxyl group of the quaternary ammonium lignin through the analyses of XRD, SEM and FT-IR.

Keywords

• rice straw
• quaternary ammonium lignin
• synthesis
• aucl₄^-
• adsorption properties